import { save } from "@tauri-apps/plugin-dialog";
import pkg from "../../package.json";
import { DEFAULT_PREFS, type RenderPrefsV1 } from "../pdf/model/prefs";
import { buildRenderModel } from "../pdf/model/build";
import { bankFromSnapshot, vendorFromSnapshot } from "../pdf/model/vendor";
import { initBrowserRendering } from "../pdf/render/browserInit";
import { renderInvoicePdf as renderModelPdf, type RenderInvoiceResult } from "../pdf/render/invoice";
import { api } from "./api";
import { imageSizeFromDataUri } from "./imageSize";
import type { InvoicePdfProps } from "./pdfProps";
import type { BankAccount, Invoice, Settings } from "./types";

function bytesToBase64(bytes: Uint8Array): string {
  let bin = "";
  const step = 0x8000;
  for (let i = 0; i < bytes.length; i += step) bin += String.fromCharCode(...bytes.subarray(i, i + step));
  return btoa(bin);
}

/** Flat props for the on-screen preview; the PDF itself is built by renderInvoicePdf. */
export async function buildPdfProps(
  invoice: Invoice,
  settings: Settings,
  bank: BankAccount | null,
): Promise<InvoicePdfProps> {
  // Re-exports use the vendor details frozen at issue; live settings are only a fallback for
  // legacy rows without a snapshot.
  const vendor = vendorFromSnapshot(invoice.vendorSnapshot, settings);
  const logoDataUri = vendor.logoPath ? await api.readAssetDataUri(vendor.logoPath) : null;
  const signatureDataUri = invoice.signaturePath
    ? await api.readAssetDataUri(invoice.signaturePath)
    : null;

  const resolvedBank = bankFromSnapshot(invoice.bankSnapshot, bank);

  return {
    vendor,
    bank: resolvedBank,
    logoDataUri,
    signatureDataUri,
    number: invoice.number,
    invoiceDate: invoice.invoiceDate,
    dueDate: invoice.dueDate,
    clientName: invoice.clientName,
    clientAddress: invoice.clientAddress,
    clientGstin: invoice.clientGstin,
    poNumber: invoice.poNumber,
    placeOfSupplyStateCode: invoice.placeOfSupplyStateCode,
    items: invoice.items,
    subtotal: invoice.subtotal,
    discount: invoice.discount,
    taxType: invoice.taxType,
    taxRate: invoice.taxRate,
    cgst: invoice.cgstAmount,
    sgst: invoice.sgstAmount,
    igst: invoice.igstAmount,
    total: invoice.total,
    amountInWords: invoice.amountInWords,
    notes: invoice.notes,
  };
}

/** A logo with no readable size is fitted as if it filled Classic's 170 x 54 box. */
const UNKNOWN_LOGO_SIZE = { width: 170, height: 54 };

/**
 * Renders an issued invoice through the engine: model (supplier and bank from the snapshots frozen at
 * issue, live settings only as a fallback) -> frame -> template -> PDF bytes, with the layout audit
 * issues and fingerprint.
 */
export async function renderInvoicePdf(
  invoice: Invoice,
  settings: Settings,
  bank: BankAccount | null,
  prefs: RenderPrefsV1 = DEFAULT_PREFS,
): Promise<RenderInvoiceResult> {
  await initBrowserRendering();
  const vendor = vendorFromSnapshot(invoice.vendorSnapshot, settings);
  const logoUri = vendor.logoPath ? await api.readAssetDataUri(vendor.logoPath) : null;
  const signatureDataUri = invoice.signaturePath ? await api.readAssetDataUri(invoice.signaturePath) : null;
  const model = buildRenderModel({
    invoice,
    vendor: settings,
    bank,
    logo: logoUri ? { dataUri: logoUri, ...(imageSizeFromDataUri(logoUri) ?? UNKNOWN_LOGO_SIZE) } : null,
    signatureDataUri,
    appVersion: pkg.version,
  });
  return renderModelPdf({ model, prefs });
}

/** Asks for a save location and writes the bytes there; null when the dialog is cancelled. */
export async function savePdfBytes(bytes: Uint8Array, fileName: string): Promise<string | null> {
  const suggested = fileName.replace(/[^A-Za-z0-9._-]+/g, "-") || "invoice";
  const path = await save({
    defaultPath: `${suggested}.pdf`,
    filters: [{ name: "PDF document", extensions: ["pdf"] }],
  });
  if (!path) return null;
  await api.saveBinaryFile(path, bytesToBase64(bytes));
  return path;
}

export async function exportInvoicePdf(
  invoice: Invoice,
  settings: Settings,
  bank: BankAccount | null,
  prefs: RenderPrefsV1 = DEFAULT_PREFS,
): Promise<string | null> {
  const { bytes } = await renderInvoicePdf(invoice, settings, bank, prefs);
  return savePdfBytes(bytes, invoice.number);
}